An intrapericardial aneurysm of the left atrial wall in a 28-year-old man is reported. This is a rare congenital anomaly. The patients are usually identified by clinical signs, when complications such as cardiac arrhythmias and systemic embolism occur. Clinical findings including the ECG are non-specific. Cardiomegaly and unusual configuration of the heart are consistantly found, but are not pathognomonic. The diagnosis is usually confirmed by angiocardiography. Echocardiography, computed tomography and/or MRI can contribute to the diagnosis. Operation seems to be indicated if complications are to be avoided.